function display(id, wartosc, czas)
{
  clearTimeout(display_timer_id[id]);
  if (document.getElementById) display_timer_id[id] = setTimeout('document.getElementById("' + id + '").style.display = "' + wartosc + '"', czas);
  else if (document.all) display_timer_id[id] = setTimeout('document.all["' + id + '"].style.display = "' + wartosc + '"', czas);
}

function liczba_add2(f){
var numer=f.add2.value;
if (isNaN(numer)){
alert("You should use digits in field marked [^]");
return false;
}
return true;
}

function liczba_add4(f){
var numer=f.add4.value;
if (isNaN(numer)){
alert("You should use digits in field marked [^]");
return false;
}
return true;
}

function checkForm(f){
var numer2=f.add2.value;
var numer4=f.add4.value;	
if (isNaN(numer2) || isNaN(numer4)){
alert("You should use digits in field marked [^]");
return false;
}
return true;
}